The aim of this project is the identification of molecules that specifically target Gs mutations, both as probes for the study of the altered signaling as well as the basis for the development of drugs to treat FD/MAS and other disorders arising from Gs mutations. During this period, the collaborative team developed a medicinal chemistry plan, starting from a previously identified singleton hit. Structure activity relationship (SAR) studies have begun, and an extensive group of compounds has been synthesized to probe different regions of the hit molecule. Testing of the newly synthesized molecules in a panel of relevant Gsa assays is currently underway.